This disclosure relates generally to the field of image and video processing. More specifically, this disclosure relates to preserving detail in low-light scenes.
A video coder may code frames of a source video sequence into a coded representation that has a smaller bit rate than the source video. The video coder may code processed video data according to any of a variety of different coding techniques to achieve compression. The resulting compressed video sequence may be transmitted to a decoder via a channel (e.g., wireless network). To recover the video data, the transmitted compressed video sequence may be decompressed at the decoder by inverting the coding processes performed by the coder, yielding a recovered video sequence.
After the compressed video sequence is decoded, a variety of undesired coding artifacts may be seen in the frames of the video sequence. The coding artifacts may include loss of details, blockiness, ringing, aliasing, posterizing and banding. These artifacts may be introduced due to preprocessing performed on the frames of the video sequence (e.g., noise filtering) and/or lossy data compression performed by the video coder. For example, banding may be introduced when the number of bits used to represent image data in a region of a frame is reduced. The reduced number bits that are available to represent a region may be insufficient to display every shade in the region of the frame. In video coder/decoder systems banding may be introduced when the video coder assigns a low number of bits to regions of a frame that have little detail, low contrast, dark regions and/or little noise.